1. Field of the Invention
The present invention relates to a collimator and a method of producing a collimator for a scintillator.
2. Discussion of the Background
In recent diagnosis of diseases, much weight is given to the role of an imaging diagnosis using an X-ray photograph, an X-ray CT image, a scintigram by radio isotope (RI), an ultrasonic image, a positron CT image, a thermogram, a nuclear magnetic resonance (NMR) image, or the like. Of those, the RI-oriented scintigram is an extracted image of RI in a body. A scinticamera is a device for acquiring such a scintigram. This scinticamera detects radiation given in a body by a large circular scintillator, a number of photomultiplier tubes, a computer, etc. A honeycomb perforated collimator is provided next to the scintillator to detect radiation from a target organ as much as possible at high sensitivity.
Such a collimator has, for example, 2000 to 4000 regular hexagonal holes regularly formed therein, and is made of lead. The axes of these holes are set to be normal to a focus line. These holes are formed by setting taper pins with a regular hexagonal cross section upright, introducing melted lead and pulling out the taper pins after the lead becomes solid. It is desirable that septa constituting boundary portions of the holes are thinner (equal to or less than 0.2 mm) in order to improve the resolution. If the thicknesses of septa are set equal to or less than 0.2 mm, however, a molten metal may not stir at the time of casting or the holes may be deformed or the septa may be damages when pulling out the pins. Furthermore, the collimator having even one defective portion cannot be used as a product and is difficult to repair, thus significantly reducing the yield.